Since 1999, labor pain control has being performed in China, and the initial time of analgesia is at the cervix >= 2 cm. Meanwhile, American Society of Obstetrics & Gynecology recommended that the labor analgesia with neuraxial block should be performed at the cervix >= 4 cm in 2002. After that, the threshold has been revised to at least >= 2 cm in 2006 by the Society. However, in China, the practice of labor analgesia with neuraxial block has being performed for over seven years. Up until now, the practice has being experienced during this ten-year period at the cervix around 1 cm. The investigators hypothesized that labor pain control in different stages had different characteristics and had different influence on patients short- and long-lasting outcomes. This study is mainly investigating different labor analgesia procedures in different stages since the initiation of the practice in 1999, and assessing their influence on the outcomes to display the trajectory of development of labor analgesia in China of which might fit to the the whole process of the study of labor analgesia throughout the world. All these were done by analyzing the data records since from January 1999 to December 2008.

Inclusion Criteria:

• Parturients used labor analgesia

Exclusion Criteria:

• Following criteria were based on the records of information received from the ten-year practice screened by investigators:

  1. Chronic pain and psychiatric diseases records
  2. Participants younger than 18 years or older than 45 years
  3. Alcohol addictive or narcotic dependent patients were excluded for their influence on the analgesic efficacy of the epidural analgesics
  4. Subjects with a nonvertex presentation or scheduled induction of labor
  5. Diagnosed diabetes mellitus and pregnancy-induced hypertension
  6. Twin gestation and breech presentation

All parturients delivered in the investigator's institution since from January 1999 to December 2008